It is common in many industries to apply various fluid materials, such as adhesives, epoxies, sealants, sound deadening materials, structurally-stiffening materials, insulating materials, and the like, using robotically-applied materials supplied from a dispensing system. These fluid materials are commonly applied to a wide variety of items, such as (but not limited to) automotive parts, household appliance parts, conformal coating of electronic circuit boards, medical devices, and construction items (windows, doors, etc.) during manufacture.
One known method of applying fluid materials to a work piece involves extruding the fluid material. Extrusion of fluid material generally involves maintaining an outlet nozzle of an extruding device very close to the work piece and allowing a single bead of fluid material to be applied to the work piece, either as the work piece is moved relative to the nozzle or the nozzle is moved relative to the work piece.
Another known method of applying a fluid material to a work piece is to “stream” the fluid material. “Streaming” is a relatively high-speed application process wherein the fluid material is dispensed from a nozzle under relatively high pressure and from a relatively greater distance from the work piece as compared to methods where the fluid material is extruded onto the work piece. Generally, a work piece is set in position—either robotically, via a conveyor system, or manually—and a fluid dispensing nozzle mounted to the end of a robot arm is caused to make one or more “passes” over the work piece, dispensing fluid material during each pass. Known systems for streaming fluid materials, such as that disclosed in U.S. Pat. No. 5,979,794 to DeFillipi et al., include a nozzle having a single outlet orifice for dispensing a single stream of fluid material. As a result, each pass of the dispensing mechanism over the work piece produces a single bead of fluid material that is approximately the width of the outlet orifice opening of the nozzle.
Many situations require the application of relatively wide bands, i.e., several inches wide, of fluid material to a work piece. By way of example only, various automotive sound dampening applications require the application of wide bands of sound dampening material or panel-stiffening material to a vehicle door, body panel or frame assembly. Because the outlet orifice of a streaming nozzle must maintain a relatively small diameter (to maintain the required fluid pressure to stream the material), it is not possible to stream wide bands of fluid materials onto a work piece during a single pass of the robot arm using known methods and systems for fluid streaming. Accordingly, for situations requiring wide bands of fluid materials, various application methods have been used.
One known method is to cause the application nozzle to make several passes over the work piece, thereby applying several beads or streams of fluid material adjacent each other. This method suffers from several disadvantages. First, because this method typically requires many passes by the application nozzle, the manufacturing process is slowed to accommodate the amount of time required to physically move the nozzle back and forth over the work piece until the entire band is applied. Second, it has been found to be difficult to create a continuous band of material using this method because it is difficult to ensure that adjacently-applied beads are the same thickness and that they are applied precisely adjacent to each other. Third, the automation tooling experiences additional wear and tear due to the additional motion required in making multiple passes over the work piece. Fourth, it is more complicated and less efficient to program equipment to make multiple passes over the work piece instead of a single pass. Further, because fluid materials being applied to the work piece tend to “set up” relatively quickly, a previously-applied bead may not blend together with a subsequently-applied bead particularly well, thus resulting in distinct beads of material instead of a continuous band of material on the work piece.
Another known method of applying fluid material to create a relatively wide band on a work piece is known as “swirling.” Swirling application systems include a single orifice nozzle that can be programmed to rotate in a circular motion. The rotating nozzle creates a circular pattern of fluid material on the work piece. As the nozzle is moved longitudinally across the work piece, the adjacent circles of material blend together to create a material band having a width equal to the diameter of the circles. Swirling systems suffer from some of the same disadvantages as described above. Further, the swirling method is sometimes imprecise, whereby “overspray” is caused as a result of the circular motion of the nozzle. Also, the width of the band of fluid material that can be created using the swirling method is relatively limited, which may result in the need for multiple passes over the work piece to achieve a desired band width. Finally, the rotating nozzle of a swirling device is actuated by a motor and other moving mechanical parts, which require significant maintenance. As a result of several of these drawbacks, the swirling method is a relatively expensive process.
Yet another known method for applying fluid material to create a wide band of material on a work piece is known as the “slot nozzle” method. The slot nozzle method involves applying fluid material using a nozzle having a single elongated orifice in the shape of a slot. While the slot nozzle method may be useful for applying wide bands of material, it has been found difficult to maintain a consistent thickness across the band of material when using a slot nozzle. The fluid material tends to accumulate closer to the middle of the band, thereby creating a band that is thicker in the middle and thinner near the edges. Further, because slot nozzles have a large continuous outlet opening, it is difficult to create sufficient fluid pressure in the system to dispense the material onto the work piece. Finally, the large outlet opening tends to allow a certain amount of fluid dripping for a period of time after the flow of fluid material is stopped.
Yet another known method for applying fluid material to create a wide band of material on a work piece is known as the “spraying” method. The spraying method involves applying fluid material using a spray nozzle having a single small orifice specifically designed to atomize the fluid material. This method suffers from several disadvantages. First, while the spraying method may be useful for applying wide bands of material, it is difficult to maintain a consistent thickness across the band of material using this method. Second, it is difficult to control the overspray created by this method. Third, the spray nozzle experiences excessive wear in a relatively short period of time as a result of the large volume of material that passes through a single spray nozzle orifice. Finally, the sprayed material particles can become airborne and contaminate Class A paint surfaces.
Perhaps as a result of the limitations associated with applying fluid materials to a work piece, the standard method of applying certain materials does not involve applying a fluid material at all. For example, it is common to apply sound deadening materials and body-stiffening materials to automotive vehicle assembly such as door panels in the form of pre-die-cut melt pads. These pads are designed to be manually applied “stuck” to a vehicle body part or door panel, and then, during a subsequent “bake” stage of the manufacturing process, the high heat causes the melt pads to melt and permanently bond to the desired work surface. The use of pre-cut melt pads is undesirable because it is very labor intensive and also necessary to maintain an inventory of special melt pads in a variety of shapes and sizes. Maintaining an inventory of several different parts is difficult and this entire method is expensive. Further, any melt pads that are unused (because of body style changes, for example) become waste.
The inventors hereof have recognized that it would be desirable to have a device and method to facilitate the application of applying various fluid materials onto a work piece in a relatively wide band and generating a variety of shapes and patterns. Further, the inventors have recognized that it would be desirable to have a device and method that would avoid the use of pre-cut melt pads.